Method of sizing paper



METHOD 9F SIZlNG PAPER Cyrus A. Weisgerher, Chadds Ford, Pa., and James W. Davis, Wilmington, Del., assignors to Hercules Powder Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Feb. 27, 1957, Ser. No. 642,650

3 Claims. (Cl. 162158) This invention relates to improvements in the internal sizing of paper with aqueous ketene dimer emulsions.

It is known that ketene dimers are effective sizing agents for paper. These materials, as such, are insoluble in water and, in order to facilitate their use in the paper industry, they have been mixed with emulsifying agents which make them readily dispersible in water for the formation of aqueous emulsions. These emulsions, however, are usually nonionic and when used for the internal sizing of paper, the retention of the ketene dimer by the cellulose fibers is not complete, with the result that some of the material goes to waste with the discarded white water.

A principal object of the present invention is the provision of a process for the internal sizing of paper with aqueous emulsions of ketene dimers wherein improved retention of the ketene dimer by the paper fibers is obtained with resultant economies in operation.

In accordance with the invention, it has been found that in the internal sizing of paper with ketene dimers, wherein an aqueous emulsion of ketene dimer is added to a dilute aqueous pulp suspension and the pulp then sheeted and dried, improved retention of the dimer by the paper fibers may be obtained by incorporating in the aqueous pulp suspension from about 0.01% to about 1%, and preferably from about 0.04% to about 0.1% by weight, based on the weight of pulp, of a water-dispersible quaternary ammonium salt. By virtue of this increased retention, it is possible to obtain a greater degree of sizing with the same concentration of ketene dimer or an equivalent degree of sizing utilizing a smaller concentration of ketene dimer. Moreover, a smaller amount of ketent dimer is lost with the discarded white water.

In a preferred procedure for carrying out the invention, the aqueous emulsion of ketene dimer containing the quaternary ammonium salt admixed therewith, is added to an aqueous pulp suspension, as in the beater of a papermaking system and the pulp then formed into sheets or webs in the conventional manner. Optimum results are obtained if, during sheet formation, the aqueous suspension is maintained at a pH within the range from about 4.5 to about 8 and preferably within the range from about 4.5 to about 5.5.

The quaternary ammonium salt is preferably added to the aqueous emulsion of ketene dimer in the form of an aqueous solution or dispersion and just prior to the introduction of same into the aqueous suspension of papermaking fibers. The addition should, of course, be accompanied with sufficient agitation or stirring to insure thorough admixture of the salt solution or dispersion with the aqueous emulsion.

While it is preferred, as indicated, to add the aqueous emulsion of ketene dimer and quaternary ammonium salt to the aqueous suspension of pulp in admixture with each other, it is also possible to add the two separately. Thus, the quaternary ammonium salt, preferably in the form of an aqueous solution or dispersion, may be added before, after or along with the aqueous ketene dimer emulsion.

Patented May 30, 1961 1 ice As in the case of the preferred procedure, optimum results are obtained if the pH of the aqueous pulp suspension is maintained within the indicated range.

Some sizing of the paper by the ketene dimer will usually be developed during drying of the paper web in accordance with conventional drying procedures utilized in the art. If desired, the sheet may be cured by heating to a relatively elevated temperature, say about C., for a short period of time such as about 10 or 15 minutes. However, this is not necessary as adequate sizing develops on mere standing or storage at room temperature for a day or two.

Having described the invention generally, the following examples are given in illustration but not in limitation of the invention. All parts and percentages are by weight unless otherwise specified.

EXAMPLE 1 Ten parts of alkylketene dimer, prepared from a mixture of approximately equal parts of stearic and oleic acids by forming the acid chlorides thereof and then reacting the acid chlorides with a tertiary amine, were mixed with 2 parts of Atlox G1096 (sorbitol-ethylene oxide condensate), a product of the Atlas Powder Company, the mixture heated to about 130 F., and then poured slowly into 488 parts of water at 130 F. to form an aqueous emulsion.

A portion of the ketene dimer emulsion was mixed with Arquad 2C (dicocodimethyl ammonium chloride), a commercial product of Armour and Co., which had been diluted with water, and the mixture of ketene dimer emulsion and Arquad 2C added to an unbleached kraft pulp, the proportions of ingredients being such as to provide 0.2% of the ketene dimer based on the pulp and 0.04% of dicocodimethyl ammonium chloride based on the pulp. The unbleached kraft pulp had been beaten to 750 SR freeness and then diluted in the proportioner of a Noble and Wood handsheet machine to a concentration of 0.25%.

One thousand parts of the thus-treated pulp were diluted to 10,000 parts in the deckle box of the handsheet machine and then formed into 8 x 8 handsheets having a basis weight of 40 lb. (24 x 36--500). A series of 12 sheets was made in this manner and with the exception of the first sheet, each successive sheet was diluted with white water drained away from the preceding sheet.

The sheets were dried on a steam roll and then cured at C. for about 10 minutes and sheets 1, 5, 10, 11 and 12 were tested for sizing by noting the time in seconds for about 50% penetration of a sheet floating on Standard Feather Ink. The sizing in each case was in excess of 600 seconds. Similar tests made on sheets which had been prepared in the same manner except for the dicocodimethyl ammonium chloride gave substantially lower sizing results, thus indicating a lower degree of retention.

EXAMPLES 2-5 The procedure of Example 1 was repeated except that the amount of quaternary ammonium salt was varied.

The results are set forth in Table I below.

Table I Alkyl- Arquad Sizing Example ketene 20, No. Dimer, Per- Pcrcent Sheet Sheet Sheet Sheet Sheet cent 1 5 10 11 12 Sheets prepared and tested in the same manner except that no Arquad 2C is used gi-ve substantially lower sizing results thus indicating a lower degree of retention.

EXAMPLES 6-10 The procedure of Example 1 was followed except that varying amounts of Triton X-400 (stearyl benzyl dimethyl ammonium chloride) were substituted for the Arquad 2C. Triton X-400 is a quaternary ammonium salt sold by Rohm & Haas Company. The results are set forth in Table 11 below.

Sheets were prepared and tested in the same manner as those in Examples 6-10 except that the amount of Triton X-400 was so small as to have little or no beneficial effect on sizing. The maximum sizing obtained was with sheet 11 which was sized to the extent of about 100 seconds.

EXAMPLE 11 This example is based on data obtained from actual mill tests utilizing Weyerhaeuser bleached kraft pulp. An aqueous nonionic emulsion of alkylketene dimer containing a known amount of oil soluble red dye was added to the paper machine chest at the rate of 12 pounds per ton of dry fiber. A sheet having a basis weight of 40 pounds was made in the usual manner. A second test was conducted in which an aqueous nonionic emulsion of alkylketene dimer containing a known amount of oil soluble red dye was added to the machine chest at the rate of pounds per ton of dry fiber and Arquad 20 was added at the fan pump at the rate of 2 pounds per ton of dry pulp. In this case the paper was made in the usual manner at pH 5. I

The amounts of ketene dimer retained by the sheets in each case were then determined by extracting the sheets with solvent to remove the dye and then comparing spectrophotometrically the dye in the extract with the dye in solutions of known concentration. The results obtained showed that the retention of ketene dimer in the second test was more than twice that in the first test.

The ketene dimers which are particularly useful in the process of the present invention are dimers having the formula [RCH=C-=O] .where R is a hydrocarbon radical, such as alkyl having at least 8 carbon atoms, cycloalkyl having at least 6 carbon atoms, aryl,varalkyl .and alkaryl. In naming ketene dimers, the radical R is named followed by ketene dimer. Thus, phenyl ketene dimer is benzyl ketene dimer is:

and decyl ketene dimer is: [C H --CH=C:O] Representative ketene dimers whose emulsions may be used in the process of the instant invention include octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, docosyl, tetracosyl, phenyl, benzyl, fl-naphthyl and cyclohexyl ketene dimers, as well as the ketene dimers prepared from montanic acid, naphthenic acid, A -decylenic acid, A -dodecylenic acid, palmitoleic acid, oleic acid, ricinoleic acid, petroselinic acid, vaccenic acid, linoleic acid, linolenic acid, eleostearc acid, licanic acid, pa- Iinaric acid, tariric acid, gadoleic acid, arachidonic acid, cetoleic acid, erucic acid and selacholeic acid, as well as ketene dimers prepared from naturally occurring mixtures of fatty acids, such as those mixtures found in coconut oil, babassu oil, palm kernel oil, palm oil, olive oil, peanut oil, rape oil, beef tallow, lard (leaf) and whale blubber. Mixtures of any of the above-named fatty acids with each other may also be used.

Aqueous emulsions of alkylketene dimers suitable for use in the process of the present invention are fully described in US. Patent No. 2,627,477 to William Downey. However, particularly preferred are those emulsions which are prepared using a nonionic emulsifier. In addition to the nonionic emulsifiers specifically disclosed by Downey, those nonionic emulsifiers which have been found to be particularly useful include polyoxyethylene sorbitan trioleate, sold by the Atlas Powder Company under the name Tween polyoxyethylene sorbitol hexaoleate, sold by the Atlas Powder Company under the trade name Atlox 1086; polyoxyethylene sorbitol laurate, sold by the Atlas Powder Company under the trade name Atlox 1045; and polyoxyethylene sorbitol oleate-laurate, sold by the Atlas Powder Company under the trade name Atlox 1045A.

The aqueous emulsions and/or suspensions are added to the paper pulp in amounts such as to produce a concentration of the ketene dimer in the aqueous pulp suspension of from about 0.01% to about 1% by weight based on the weight of dry pulp. The preferred concentration is from about 0.1% to about 0.5 by weight based on the weight of dry pulp.

Any of the cationic water-soluble or water-dispersible quaternary ammonium salts may be utilized in the process of the present invention. Preferred compounds of this class are those having the following formulas:

where X is halogen, R is a small alkyl radical having from about 1 to 4 carbon atoms and R and R are selected from the group consisting of larger alkyl radicals having from about 10 to 20 carbon atoms, aryl, aralkyl and alkaryl radicals. Particularly preferred are the compounds represented by Formula 2. Typical compounds of this type are: (a) Arquad 2C in which R is methyl and R R is a mixture of alkyl groups obtained from the acids of coconut oil and contain predominantly dodecyl, tetradecyl and hexadecyl groups, and (b) Triton X- 400 in which R is octadecyl, R is benzyl and R is methyl. Representative of other water-soluble or waterdispersible quaternary ammonium salts which may be used are dioctadecyl dimethyl ammonium chloride, dioctadecyl methyl ethyl ammonium chloride, dioctadecyl diethyl ammonium chloride, dioctadecyl propyl methyl ammonium chloride, dioctadecyl propyl ethyl ammonium chloride, dioctadecyl dipropyl ammonium chloride, dihexadecyl dimethyl ammonium chloride, dihexadecyl methyl ethyl ammonium chloride, dihexadecyl diethyl ammonium chloride, dihexadecyl propyl methyl ammonium chloride, dihexadecyl propyl ethyl ammonium chloride, dihexadecyl dipropyl ammonium chloride, ditetradecyl dimethyl ammonium chloride, ditetradecyl methyl ethyl ammonium chloride, ditetradecyl diethyl ammonium chloride, dietetradecyl propyl methyl ammonium chloride, ditetradecyl propyl ethyl ammonium chloride, ditetradecyl dipropyl ammonium chloride, didodecyl dimethyl ammonium chloride, didodecyl methyl ethyl ammonium chloride, didodecyl diethyl ammonium chloride, didodecyl propyl methyl ammonium chloride, didodecyl propyl ethyl ammonium chloride, didodecyl dipropyl ammonium chloride, benzyl octadecyl dimethyl ammoniurn chloride, benzyl octadecyl methyl ethyl ammonium chloride, benzyl octadecyl diethyl ammonium chloride, benzyl octadecyl propyl methyl ammonium chloride,

benzyl octadecyl propyl ethyl ammonium chloride, benzyl octadecyl dipropyl ammonium chloride, phenyl octadecyl dimethyl ammonium chloride, phenyl octadecyl methyl ethyl ammonium chloride, phenyl octadecyl diethyl ammonium chloride, phenyl octadecyl propyl methyl ammonium chloride, phenyl octadecyl propyl ethyl ammonium chloride, phenyl octadecyl clipropyl ammonium chloride, phenyl ethyl octadecyl dimethyl ammonium chloride, phenyl ethyl octadecyl methyl ethyl ammonium chloride, phenyl ethyl octadecyl diethyl ammonium chloride, phenyl ethyl octadecyl propyl methyl ammonium chloride, phenyl ethyl octadecyl propyl ethyl ammonium chloride, phenyl ethyl octadecyl dipropyl ammonium chloride, benzyl trimethyl ammonium chloride, cyclohexyl trimethyl ammonium chloride and phenyl trimethyl ammonium chloride.

In the practice of the invention, still further improvements in retention and sizing may be obtained if the aqueous pulp suspension to which the ketene dimer emulsion and quaternary ammonium salt are added contains a small amount, i.e., from about 0.2% to about 4% by weight based on the weight of pulp, of an acid salt. The invention, therefore, contemplates the prior addition to the aqueous pulp suspension of from about 0.2% to about 4%, and preferably from about 0.5% to about 2%, based on the weight of pulp, of an acid salt. Alum is particularly preferred for this purpose although other acid salts such as ferric chloride, titanium tetrachloride, zirconium sulfate and the like may be used.

The mixtures and/or additives herein disclosed may be used in combination with various additives conventionally used in papermaking such as wet-strength resins, fillers and pigments, adhesives and the like.

It will thus be seen that the process of the present invention provides improvements in the internal sizing of paper with aqueous ketene dimer emulsions. While preferred embodiments of the invention have been disclosed, the invention is not to be construed as limited by the specific details described except as they may be included in the following claims.

What we claim and desire to protect by Letters Patent is:

1. The process of sizing paper which comprises forming an aqueous suspension of paper pulp, admixing with th aqueous suspension of paper pulp a preformed aqueou ketene dimer emulsion to which has been added after formation of the emulsion a cationic water-dispersible quaternary ammonium salt, the aqueous ketene dimer emulsion being added in an amount such that the concentration of ketene dimer in the aqueous suspension of paper pulp is from about 0.01% to about 1% based on the dry weight of pulp, the concentration of quaternary ammonium salt in the aqueous pulp suspension being from about 0.01% to about 1% based on the dry weight of pulp, the ketene dimer having the formula [RCH=C=O] where R is a hydrocarbon radical selected from the group consisting of alkyl groups having at least 8 carbon atoms, cycloalkyl having at least 6 carbon atoms, aryl, aralkyl and alkaryl groups, and the quaternary ammonium salt being selected from those having the following formulas:

where X is halogen, R is an alkyl group having from about 1 to 4 carbon atoms and R and R are selected from the group consisting of alkyl radicals having from about 10 to 20 carbon atoms, aryl, aralkyl and alkaryl.

2. The process of claim 1 wherein from about 0.2% to about 4% by weight, based on the weight of pulp, of an acid salt is added to the aqueous suspension of paper pulp prior to the addition thereto of the alkylketene dimer emulsion and the quaternary ammonium salt.

3. The process of claim 2 wherein the acid salt is alum.

References Cited in the file of this patent UNITED STATES PATENTS 2,433,802 West Dec. 30, 1947 2,654,729 Price Oct. 6, 1953 2,765,228 Jordon Oct. 2, 1956 2,785,067 Osberg Mar. 12, 1957 2,838,397 Gruntfest et al June 10, 1958 OTHER REFERENCES Zimmerman and Lavine: Handbook of Material Trade Names, Industrial Research Service, Dover, NH. (1953), pages and 66 relied on. 

1. THE PROCESS OF SIZING PAPER WHICH COMPRISES FORMING AN AQUEOUS SUSPENSION OF PAPER PULP, ADMIXING WITH THE AQUEOUS SUSPENSION OF PAPER PULP A PREFORMED AQUEOUS KETENE DIMER EMULSION TO WHICH HAS BEEN ADDED AFTER FORMATION OF THE EMULSION A CATIONIC WATER-DISPERSIBLE QUARTERNARY AMMONIUM SALT, THE AQUEOUS KETENE DIMER EMULSION BEING ADDED IN AN AMOUNT SUCH THAT THE CONCENTRATION OF KETENE DIMER IN THE AQUEOUS SUSPENSION OF PAPER PULP IS FROM ABOUT 0.01% TO ABOUT 1% BASED ON THE DRY WEIGHT OF PULP, THE CONCENTRATION OF QUARTERNARY AMMONIUM SALT IN THE AQUEOUS PULP SUSPENSION BEING FROM ABOUT 0.01% TO ABOUT 1% BASED ON THE DRY WEIGHT OF PULP, THE KETENE DIMER HAVING THE FORMULA (RCH=C=O)2 WHERE R IS A HYDROCARBON RADICAL SELECTED FROM THE GROUP CONSISTING OF ALKYL GROUPS HAVING AT LEAST 8 CARBON ATOMS, CYCLOALKYL HAVING AT LEAST 6 CARBON ATAOMS, ARYL, ARALKYL AND ALKARYL GROUPS, AND THE QUARTERNARY AMMONIUM SALT BEING SELECTED FROM THOSE HAVING THE FOLLOWING FORMULAS: 